Protein is an essential component of the diet of all domestic animals and is necessary for growth, body maintenance, the production of young and the output of meat and non-meat products e.g., milk, eggs and wool. Thus, for productive animal agriculture, protein is essential.
The protein, and hence amino acid requirements for most agriculturally important animals are well known in the art (see e.g., The Encyclopedia of Farm Animal Nutrition, M. F. Fuller (ed) 2004, Cabi Publishing). As is known in the art, requirements vary depending on the species and age of animals. For example, pastures and forage can play a major role in supplying ruminants with their protein needs, because the biota of ruminant animals synthesize amino acids and proteins de novo. But for some species e.g., fish, the provision of adequate nutrition, especially adequate protein, must come directly from the diet.
The raising of fish in aquaculture presents nutritional issues that are unique amongst agricultural animals. In particular, the protein allowances in fish diets are appreciably higher than those in the diets of terrestrial warm-blooded animals. Thus, aquaculture feeds characteristically contain a higher percent of protein than feeds used in agriculture to feed e.g., poultry, swine, and beef. However, it is not just the amount of protein that makes aquaculture feeds unique, but also the requirement for high quality protein (see e.g., J. W. Hertrampf, et al. (2000) Handbook on Ingredients for Aquaculture Feeds, Kluwer Academic Publishers; and Nutrient Requirements of Fish, Committee on Animal Nutrition, Board on Agriculture, National Research Council National Academy Press (1993)).
Aquaculture is the fastest growing food production sector in the world. Thus, addressing the needs of aquaculture practices promises to improve food and nutrition for the future of humanity. The biggest need in aquaculture is to provide feeds which supply sufficient high quality protein in a palatable form.
Aquaculture feeds typically comprise fishmeal as a source of protein. Unfortunately however, in recent years, the cost of fishmeal has increased, concerns have been raised about the residues of toxic pollutants e.g., dioxin, in fishmeal, regulation of nutrients in hatchery effluents has intensified, and questions regarding the sustainability of fishmeal as an aquafeed ingredient have arisen. Thus, there is increased interest in finding alternatives to fishmeal that could be used either alone or in combination with fishmeal to provide nutritious aquaculture diets (see e.g., Hites, R. A. et al. (2004) Science 303: 226-229; Naylor, R. L. et. al. (2000). Nature 405: 1017-1024).
There are many possible sources of protein for aquaculture rations. Dietary protein can be derived from either or both plant and animal sources, but the choice of protein source must be carefully selected in order to provide high quality protein in a correct amount and with the appropriate balance of essential amino acids. The protein must be digestible and thus, bioavailable to the fish, and finally, since fish can be picky eaters, protein sources must also be palatable.
There are many possible sources of plant protein for livestock rations and naturally, grains and plant derived proteins have been considered as an alternative to fishmeal in aquaculture diets. Unfortunately however, protein concentration of plant sources are typically lower than fish meal, essential amino acids are lacking, protein digestibility may be poor and palatability of feeds prepared with plant derived proteins may be unpalatable to fish. Because of their relatively high protein concentration relative to other plant sources, soybeans and soybean meal have been extensively evaluated and are now used in aquaculture feeds particularly for non carnivorous species of farmed fish. (see e.g., Hardy, R. W. (2003) Use of soybean meals in diets of salmon and trout. Technical review paper, Managed Aquaculture Program, United Soybean Board, American Soybean Association. available through: American Soybean Association Headquarters, 12125 Woodcrest Executive Drive, Suite 100 St. Louis, Mo. 63141-5009) However, soy contains anti-nutritional compounds e.g., phytate, and/or undigestable carbohydrates e.g., oligosaccharides, and these anti-nutritional compounds limit the use of soy derived proteins in aquaculture feeds. This is a particular issue with feeds for species such as trout and salmon (see e.g., Knudsen, D., et al. (2007) Journal of Agriculture and Food Chemistry 55: 2261-2267; Knudsen, D., et al. (2006). Journal of Agriculture and Food Chemistry 54:6428-6435.
Thus, there exists a need in the art for plant based sources of high quality protein that is suitable for use in inter alia, aquaculture feeds. Fortunately, as will be clear from the following disclosure, the present invention provides for this and other needs.